The invention relates to a method of removing mercury from a mercury-containing flue gas that may also contain dust, further heavy metals and further gaseous noxious gas components, especially flue gas from a refuse incinerator; the mercury, using an alkali sulfide solution, especially sodium sulfide solution, and in particular sodium tetrasulfide solution, is converted to mercury sulfide and the mercury sulfide is precipitated out via a dust separator.
Such a method is known from DE 44 37 781 A1, where an aqueous sodium tetrasulfide solution is conveyed to the flue gas immediately after a partial removal of dust from the flue gas in an electrostatic precipitator, i.e. at a relatively high temperature, and thereafter separating off in a fabric filter the mercury sulfide that is formed by precipitation of ionic mercury Hg.sup.2++ and Hg.sup.+ and from metallic mercury Hg.sup.0. A scrubbing out of aqueous, gaseous noxious components such as HCl and SO.sub.2 is subsequently effected. With the known method, the sodium tetrasulfide solution is sprayed in with the aid of cold atomizing air at room temperature. Relatively large quantities of sodium tetrasulfide were needed for the separation of the mercury. A relatively long contact stretch is required since the sodium tetrasulfide is activated only in the hot flue gas.
It is the object of the present invention to provide a method of the aforementioned type where the mercury separation is improved by means of the introduced alkali sulfide solution, especially sodium sulfide solution.